Expansion valve

ABSTRACT

To improve the manufacturing efficiency of a body, and reduce the manufacturing cost of an expansion valve. A body accommodating a valve section is formed, using forming dies, such as die-casting dies, integrally with an inlet port for introducing refrigerant, an outlet port for delivering expanded refrigerant, a male thread, and has a power element connected thereto by the male thread. This eliminates a necessity of subjecting the body to fabrication, for forming the inlet port, the outlet port, a valve hole, a hole for receiving therein a valve element and set value-adjusting members, a hole for receiving therein a shaft which transmits an actuating force dependent on temperature sensed by the power element to the valve element, and further the male screw. Therefore, the manufacturing efficiency of the body is improved, and the manufacturing cost of the expansion valve can be reduced.

CROSS-REFERENCE TO RELATED APPLICATIONS, IF ANY

This application claims priority of Japanese Application No. 2006-157946 filed on Jun. 7, 2006 and entitled “EXPANSION VALVE”.

BACKGROUND OF THE INVENTION

(1) Field of the Invention

The present invention relates to a mounting structure of an expansion valve, and more particularly to an expansion valve configured to expand high-temperature, high-pressure liquid refrigerant condensed by a condenser and deliver low-temperature, low-pressure refrigerant to an evaporator, in a refrigeration cycle of an automotive air conditioner.

(2) Description of the Related Art

In general, a refrigeration cycle of an automotive air conditioner comprises a compressor that compresses refrigerant circulating through the refrigeration cycle, a condenser that condenses the compressed refrigerant, a receiver that temporarily stores the refrigerant circulating through the refrigeration cycle and separates the condensed refrigerant into a gas and a liquid, an expansion valve that throttles and expands the liquid refrigerant obtained by gas/liquid separation, and an evaporator that evaporates the refrigerant expanded by the expansion valve. The expansion valve is implemented e.g. by a thermostatic expansion valve configured to sense the temperature and pressure of refrigerant at the outlet of the evaporator and control the flow rate of refrigerant delivered to the evaporator.

This thermostatic expansion valve includes a body formed with a first passage that passes refrigerant flowing from the receiver toward the evaporator, and a second passage that passes refrigerant returned from the evaporator to the compressor. In an intermediate portion of the first passage of the body, a valve section is disposed for controlling the flow rate of refrigerant, and a power element is disposed in the body at a location on the second passage side, for sensing the temperature and pressure of refrigerant flowing through the second passage, and controlling the valve lift of the valve section via an actuating shaft (see e.g. Japanese Unexamined Patent Publication No. 2002-115938).

Here, the body is generally made by cutting an extrusion-molded item of an aluminum alloy which is light in weight and excellent in machinability into a prism-like block to thereby prepare a half-finished solid part, and then forming the first passage, the second passage, and a portion where the power element is connected, by cutting. However, the cutting of the part takes much time, and degrades the yield from the material, which increases the manufacturing costs.

On the other hand, there has been proposed a technique of making the body e.g. by the use of blow extrusion molding (see e.g. Japanese Unexamined Patent Publication No. 10-267470). By paying attention to the fact that the aforementioned second passage may have a simple straight shape, this technique is employed to form the second passage simultaneously during the process of the extrusion molding of the body. This results in the omission of a hole-forming process to cut the second passage, the saving of the material of the aluminum alloy, and improvement of the manufacturing efficiency of the body to some extent.

However, in the above-mentioned blow extrusion molding, it is required to extrude the aluminum alloy in a fixed extruding direction and hence it can be applied only to a straight shape having a fixed cross-section. Therefore, this technique cannot be applied to the formation of the first passage in which the valve section is integrally formed in the intermediate portion thereof. Further, at respective ends of the first passage and the second passage, sealing surfaces are formed on which sealing members are provided so as to be interposed when pipes leading to the compressor, the receiver, and the evaporator are connected thereto, and the sealing surfaces are formed as the surfaces of increased-diameter portions, which makes it impossible to form them by extrusion molding. Therefore, there is no other way but to perform cutting in forming these portions, and hence there is a problem that the saving of the material and the improvement of the manufacturing efficiency are not sufficient.

Further, after forming the second passage by the blow extrusion molding, when cutting is attempted to be performed on an end thereof, using a lathe or the like, it is not easy to align the axis of the passage formed by the extrusion molding and the rotational axis during the cutting process. Therefore, when a sealing portion is formed by a tool, such as a drill, the axis of the tool can become off from the axis of the passage, so that off-centered load can be applied to the tool and the body during the cutting process, which can cause a trouble in cutting.

Further, a juncture between the body and the power element has a screwing structure, and hence is necessary to thread a portion of the body to be connected to the power element, which degrades the manufacturing efficiency, and increases manufacturing costs.

SUMMARY OF THE INVENTION

The present invention has been made in view of these points, and an object thereof is to improve the manufacturing efficiency of a body, and reduce the manufacturing cost of an expansion valve.

To solve the above problem, the present invention provides an expansion valve that passes introduced refrigerant through a valve section disposed therein to thereby throttle and expand the introduced refrigerant, wherein a body accommodating the valve section is formed, using forming dies, integrally with a thread part that connects a power element thereto.

The above and other objects, features, and advantages of the present invention will becomes apparent from the following description when taken in conjunction with the accompanying drawings which illustrate preferred embodiments of the present invention by way of example.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a central cross-sectional view showing an expansion valve according to a first embodiment.

FIG. 2 is a schematic explanatory view illustrating an essential part of the method of making a body of the expansion valve.

FIG. 3A is a plan view of the body.

FIG. 3B is a font view of the body.

FIG. 4 is a cross-sectional view of an example of mounting of the expansion valve according to the present invention.

FIG. 5 is a cross-sectional view taken on line A-A of FIG. 4.

FIG. 6 is a cross-sectional view of an expansion valve according to a second embodiment and a mounted state thereof.

FIG. 7 is a cross-sectional view taken on line B-B of FIG. 6.

FIG. 8 is a cross-sectional view of an expansion valve according to a third embodiment and a mounted state thereof.

FIG. 9 is a view of the expansion valve in the mounted state, taken from an inlet port side.

FIG. 10 is a cross-sectional view of an expansion valve according to a fourth embodiment and a mounted state thereof.

FIG. 11 is a cross-sectional view taken on line C-C of FIG. 10.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

FIG. 1 is a central cross-sectional view of an expansion valve according to a first embodiment.

The expansion valve 1 comprises a vale section 2 that controls the flow rate of refrigerant, and a power element 3. The valve section 2 includes a body 4, and the body 4 has sides integrally formed with an inlet port 5 connected to a receiver of the refrigeration cycle, for introducing high-pressure, high-temperature refrigerant, and an outlet port 6 connected to an evaporator, for delivering low-temperature, low-pressure refrigerant. In a central portion of the body 4, there are formed a valve hole 7 that passes refrigerant introduced into the inlet port 5 to the outlet port 6, such that the valve hole 7 extends in a direction orthogonal to the respective axes of the inlet port 5 and the outlet port 6. The body 4 has a hole 8, larger in diameter than that of the valve hole 7, formed therein such that the hole 8 extends downward, as viewed in FIG. 1, from the valve hole 7 through the body in the direction of the axis of the valve hole 7. The hole 8 has a valve element 9, triangular in cross-section, disposed therein, and the valve element 9 is urged by a spring 10 in the valve closing direction. The spring 10 is received by a spring-receiving member 11 press-fitted in the opening of the hole 8. The load of the spring 10 is adjusted by the press-fitted amount of the spring-receiving member 11 press-fitted into opening of the hole 8, whereby the set value of the expansion valve 1 is adjusted. The body 4 is also formed with a hole 12, slightly smaller in diameter than the valve hole 7, such that the hole 12 extends upward, as viewed in FIG. 1, from the valve hole 7 through the body in the direction of the axis of the valve hole 7. The hole 12 has a shaft 13 integrally formed with the valve element 9 disposed therein. The shaft 13 has a reduced-diameter portion at a location corresponding to an extension from the inlet port 5, thereby securing a passage through which refrigerant flows from the inlet port 5 into the valve hole 7. The shaft 13 also has a groove circumferentially formed in the periphery of a portion positioned within the valve hole 12, and a V packing 14 is provided in the groove for preventing high-pressure refrigerant introduced into the inlet port 5 from leaking to the power element 3 via a clearance between the shaft 13 and the body 4. The body 4 has a hollow cylindrical guide 15 formed on a central part of an upper portion thereof, as viewed in FIG. 1, in a manner protruding therefrom, for holding the shaft 13, and a male thread 16 is formed on the outer periphery thereof.

The power element 3 comprises an upper housing 17, and a lower housing 18, which are each in the form of a thick metal disc, a diaphragm 19 made of a flexible metal sheet and disposed in a manner partitioning a space enclosed by the housings 17 and 18, and a disc 20 disposed on a side of the diaphragm toward the valve section 2. The power element 3 is formed by welding the peripheral edges of the upper housing 17, the lower housing 18, and the diaphragm 19 to each other e.g. by TIG welding. This defines a temperature-sensing chamber enclosed by the upper housing 17 and the diaphragm 19, and the temperature-sensing chamber is filled with saturated vapor gas via a gas introducing hole 21 formed through the upper housing 17. The gas introducing hole 21 is closed e.g. by resistance-welding of a metal ball 22. Thus, the temperature-sensing chamber is formed for use in sensing the temperature of refrigerant flowing from the evaporator.

The lower housing 18 has an open central portion. The opening of the open central portion is integrally formed with a hollow cylindrical hub 23. The inside of the hub 23 is formed with a female thread for screwing onto the male thread 15 formed on the outer periphery of the guide 15. Further, the lower housing 18 has gas-passing holes 25. The gas-passing holes 25 cause refrigerant delivered from the evaporator to be introduced into space on the lower surface side of the diaphragm 19, and the amount of introduced refrigerant is adjusted by changing the size of each gas-passing hole or the number of gas-passing holes. The lower surface of the diaphragm as viewed in FIG. 1 has an end face of the shaft 13 protruding from the body 4 abutted thereagainst via the disc 20, whereby displacement of the diaphragm 19 is transmitted to the valve element 9.

The expansion valve 1 configured as described above has its body 4 formed preferably by die-casting of a metal, to dispense with fabrication such as cutting. Next, a description will be given of an essential part of the method of making the body 4.

FIG. 2 is a schematic explanatory view illustrating the essential part of the method of making the body of the expansion valve. Component elements appearing in FIG. 2, which are identical to the component elements appearing in FIG. 1, are designated by identical reference numerals.

The body 4 can be made by die-casting of an aluminum alloy, a zinc alloy, or another metal, but the following description will be given of the case of die-casting the aluminum alloy, by way of example. In the present embodiment, there is used a die-casting apparatus which includes a first die 30, a second die 40, and a third die 50, and is configured such that the first die 30 and the second die 40 are actuated by an actuator, not shown, in horizontal directions as viewed in FIG. 2, while the third actuator 50 is actuated by an actuator, not shown, in vertical directions as viewed in the same.

The first die 30 has a cavity 31 for forming a portion of the body 4 where the inlet port 5 is disposed, on a side of the first die 30 opposed to the second die 40. Within the cavity 31, a port passage-forming portion 32 is formed to protrude toward the second die 40, for forming the inlet port 5, and further, a thread-forming portion 33 is formed therein for forming half of the male thread 16. The second die 40 has a cavity 41 for forming a portion of the body 4 where the outlet port 6 is disposed, on a side of the second die 40 opposed to the first die 30. Within the cavity 41, a port passage-forming portion 42 is formed to protrude toward the first die 30, for forming the outlet port 6, and a thread-forming portion 43 is formed therein for forming half of the male thread 16. The third die 50 has a cavity 51 for forming a portion of the body 4 where the spring-receiving member 11 is press-fitted. Within the cavity 51, a hole-forming portion 52, a valve hole-forming portion 53, and a hole-forming portion 54 are formed to protrude upward, as viewed in FIG. 2, for forming the hole 8, the valve hole 7, and the hole 12, respectively. It should be noted that the first die 30, the second die 40, and the third die 50 are formed with injection passage-forming grooves, not shown, for pouring in molten aluminum alloy, and exhaust passage-forming grooves, not shown, for evacuating the cavities 31, 41, and 51, respectively, in opposed surfaces thereof, and also with insertion holes for inserting tools for releasing the casting from the dies.

In making the body 4, molten aluminum alloy is poured into the die set of the first die 30, the second die 40, and the third die 50 which are tightly fastened, via the injection holes. In the present embodiment, as the aluminum alloy, an Al—Si—Cu alloy is used which is excellent in castability. After the molten alloy solidifies, the third die 50 is pulled out downward as viewed in FIG. 2, and the first die 30 and the second die 40 are separated from each other. In doing this, the first die 30 and the second die 40 are moved in the horizontal directions while causing the releasing tools to be pushed against the casting in close contact with the first die 30 and the second die 40. Thus, by configuring the dies such that they have a three-way separable structure in which they can be moved away from each other in respective three directions, the body can be formed such that it is integrally formed with the inlet port 5, the outlet port 6, the valve hole 7, the holes 8 and 12, and the male thread 16, to thereby dispense with fabrication of the valve hole 7, the thread part, and so forth. Further, since the body 4 is formed based on the three-way separable structure of the dies, the respective axes of the inlet port 5 and the outlet port 6 can be made identical or parallel with each other, and the hole 8, the valve hole 7, and the hole 12 are disposed on the same axis in a direction orthogonal to the direction of those axes, such that they have respective inner diameters sequentially reduced in the mentioned order.

It should be noted that in the die-casting apparatus described above, the description has been given assuming the apparatus makes a single casting, but thanks to the three-way separable structure of the dies, it is possible to configure the apparatus such that a plurality of sets of the first dies 30, the second dies 40, and the third dies 50 are disposed in parallel with each other, and are simultaneously operated in the three directions, which makes it possible easily construct a die-casting apparatus which permits a plurality of castings to be obtained at a time.

FIG. 3A is a plane view of the appearance of the body. FIG. 3B is a front view of the appearance of the body.

The body 4 made by die-casting is formed with a hollow cylindrical part 5 a defining the inlet port 5 and extending in the direction of separating the first die 30, a hollow cylindrical part 6 a defining the outlet port 6 and extending in the direction of separating the second die 40, and a hollow cylindrical part 8 a defining the hole 8 and a guide 15 defining the hole 12, extending in the direction of separating the third die 50. Further, the male thread 16 formed on the outer periphery of the guide 15 is a partial thread in which portions of an outer peripheral surface of the guide 15 facing in directions at right angles to the respective directions of separating the first die 30 and the second die 40 are not threaded, and comprise a thread portion 16 a formed on an outer peripheral portion of the same facing in the direction of separating the first die 30 and a thread portion 16 b formed on an outer peripheral portion of the same facing in the direction of separating the second die 40. It should be noted that in the present embodiment, the body 4 has an extended part 4 a extended in a direction at right angles to the respective directions of separating the first die 30 and the second die 40, which, as described hereinafter, has the function of positioning the expansion valve 1, when it is incorporated in the system of the refrigeration cycled.

Next, a description will be given of an example of application of the expansion valve 1 constructed as described above, and the operation thereof.

FIG. 4 is a cross-sectional view of an example of mounting of the expansion valve according to the present invention, and FIG. 5 is a cross-sectional view taken on line A-A of FIG. 4.

The expansion valve 1 is mounted in a return low-pressure pipe which extends from the evaporator 60 to the compressor, such that the expansion valve 1 is accommodated therein in its entirety, and what is more, connection of the inlet port 5 to a high-pressure pipe 61 through which condensed liquid refrigerant is supplied and connection of the outlet port 6 via which the expanded refrigerant is delivered to an inlet pipe 62 of the evaporator 60 are established within the return low-pressure pipe.

More specifically, the evaporator 60 is integrally formed with a casing 64 e.g. by furnace brazing such the casing 64 surrounds the inlet pipe 62 and a refrigerant outlet port 63. The low-pressure pipe 65 has an end thereof welded to a joint 66 (via a portion indicated by a black triangle), and the joint 65 is hermetically connected to the casing 64 by a pipe clamp 67. The low-pressure pie 65 and the high-pressure pipe 61 are formed as a double pipe in which the high-pressure pipe 61 is coaxially arranged within the low-pressure pipe 65. It should be noted that a juncture between the inlet port 5 and the high-pressure pipe 61, a juncture between the outlet port 6 and the inlet pipe 62, and a juncture between the casing 64 and the joint 66 are sealed by respective O rings. Further, the expansion valve 1 has a heat insulation cover 68 of resin or rubber attached to the power element 3 in a manner covering the same.

The expansion valve 1 housed in the casing 64 is positioned in the center of the casing 64, and therefore, as shown in FIG. 5, the extended part 4 a of the body 4 and the heat insulation cover 68 have respective outer contours formed along the inner shape of the casing 64.

Now, the expansion valve 1 is mounted in the casing 64 functioning as a low-pressure return pipe from the evaporator 60, as follows: Since the evaporator 60 and the casing 64 are integrally welded such that the inlet pipe 62 of the evaporator 60 protrudes into the casing 64, first, an O ring is fitted on the inlet pipe 62, and then the expansion valve 1 is pushed into the casing 64 until the inlet pipe 62 is fitted in the outlet port 6. An O ring is fitted on the inlet port 5 of the expansion valve 1 in advance, or at this time. Next, the inlet port 5 is positioned such that it can be fitted in the high-pressure pipe 61, and the joint part 66 having O rings fitted beforehand in respective grooves formed by bending the end portion of the joint part 66 is pushed into the casing 64. Finally, a connecting portion of the casing 64 and that of the joint part 66 are connected by the pipe clamp 67.

Thus, the expansion valve 1 is mounted in the casing 64, with the inlet port 5 connected to the high-pressure pipe 61, and the outlet port 6 connected to the inlet pipe 62 of the evaporator 60. With this configuration, the expansion valve 1 is accommodated in the low-pressure return pipe from the evaporator 60, together with the juncture to the high-pressure pipe 61 and hence even if a minute amount of high-pressure refrigerant leaks via the O ring at the juncture due to penetration therethrough, the leaded refrigerant remains in the low-pressure return pipe but does not leak out into the atmosphere.

Next, a description will be given of the operation of the expansion valve 1. When an automotive air conditioner is in stoppage, saturated vapor gas filling the temperature-sensing chamber of the power element 3 is condensed, so that the pressure of the gas is low. Therefore, the diaphragm 19 is displaced inward, and the displacement is transmitted to the valve element 9 via the disc 20 and the shaft 13, whereby the expansion valve 1 is placed in the fully closed state.

When the automotive air conditioner is started in this state, refrigerant is drawn by the compressor, and hence pressure within the low-pressure pipe 65 drops. The power element 3 senses this, so that the diaphragm 19 is displaced outward to lift the valve element 9. On the other hand, refrigerant compressed by the compressor is condensed by a condenser, and liquid refrigerant obtained by gas/liquid separation in the receiver is supplied to the inlet port 5 of the expansion valve 1 through the high-pressure pipe 61. It should be noted that arrows appearing in the figures indicate respective directions of refrigerant flow. The high-temperature, high-pressure liquid refrigerant is expanded while passing through the expansion valve 1 and flows out as low-temperature, low-pressure gas-liquid mixture refrigerant from the outlet port 6. The refrigerant is supplied to the evaporator 60 through the inlet pipe 62, and is evaporated in the evaporator 60 to flow out from the refrigerant outlet 63. The refrigerant delivered from the evaporator 60 is returned to the compressor via the casing 64 and the low-pressure pipe 65.

The space enclosed by the diaphragm 19 of the power element 3 and the lower housing 18 of the same communicates with the inside of the casing 64 via the gas-passing holes 25, so that while refrigerant having returned from the evaporator 60 is passing through the casing 64, some of the refrigerant is introduced into the space within the power element 3, and the temperature of the introduced refrigerant is detected by the power element 3. In the early stage of the start of the automotive air conditioner, the temperature of the refrigerant returning from the evaporator 60 is high due to heat exchange with high-temperature air in a vehicle compartment, and the power element 3 senses the temperature of the refrigerant, so that the pressure within the temperature-sensing chamber becomes high. This causes the diaphragm 19 to inflate to actuate the valve element 9 in the valve opening direction, whereby the expansion valve 1 is fully opened.

As the temperature of refrigerant from the evaporator 60 becomes lower, the pressure within the temperature-sensing chamber also becomes lower. Accordingly, the diaphragm 19 is displaced inward of the temperature-sensing chamber, whereby the expansion valve 1 moves in the valve closing direction to control the flow rate of refrigerant passing therethrough. At this time, the expansion valve 1 operates to detect the temperature of refrigerant at the outlet of the evaporator 60, and controls the flow rate of refrigerant supplied to the evaporator 60 such that the refrigerant maintains a predetermined degree of superheat.

It should be noted that since the power element 3 is disposed in the low-pressure return pipe from the evaporator 60 such that the temperature of refrigerant can be detected by the entire power element 3, the power element 3 would have a very short temperature-sensing time constant due to its structure. If the temperature-sensing time constant is short, the response to a change in the temperature of refrigerant becomes so sensitive as to perform an excessive feedback correction on the operation of the valve section 2, which can result in a periodic pressure variation (hunting). To eliminate this inconvenience, the heat insulation cover 68 is provided to block the transfer of heat to the upper housing 17 to thereby increase the temperature-sensing time constant.

FIG. 6 is a cross-sectional view showing an expansion valve according to a second embodiment of the present invention and a mounted state thereof, and FIG. 7 is a cross-sectional view taken on line B-B of FIG. 6. Component elements appearing in FIGS. 6 and 7, which have functions identical to or equivalent to those of the component elements appearing in FIGS. 1 and 4, are designated by identical reference numerals, and detailed description thereof is omitted.

The expansion valve 1 a according to the second embodiment is distinguished from the expansion valve 1 according to the first embodiment, in that it has the body 4 formed such that the respective axes of the inlet port 5 and the outlet port 6 are orthogonal to each other. This body 4 is also formed by a die-casting apparatus whose dies have a three-way separable structure. In the case of the expansion valve 1 a, however, the first die 30 is configured such that it can form the extended part 4 a of the body 4 and the thread portion 16 a of the male thread 16. Further, in the body 4 of the expansion valve 1 a, the valve element 9, the spring 10 urging the valve element 9 in the valve closing direction, and the spring-receiving member 11 for receiving the spring 10 are disposed within the outlet port 6.

The expansion valve 1 a thus configured is advantageous in the case where it is arranged such that the longitudinal direction of the double pipe formed by the high-pressure pipe 61 and the low-pressure pipe 65 extending from an engine room where the compressor is disposed to the vehicle compartment where the evaporator 60 is disposed is substantially at right angles to directions in which the inlet pipe 62 of the evaporator 60 and the refrigerant outlet port 63 open.

Therefore, the return low-pressure pipe in which the expansion valve 1 a is mounted is configured to be bent at a right angle. More specifically, the evaporator 60 is integrally formed with the inlet pipe 62 and a connecting part 64 a by furnace brazing. The casing 64 is connected to the connecting part 64 a by the pipe clamp 67, and the joint part 66 is welded to an upper portion, as viewed in FIG. 6, of the casing 64. The joint part 66 is connected to the low-pressure pipe 65 by the pipe clamp 67.

The expansion valve 1 a having the body 4 configured such that the inlet port 5 and the outlet port 6 extend in the respective directions orthogonal to each other is mounted in the casing 64 and the joint part 66 having the respective openings facing in the directions orthogonal to each other, as described above. The body 4 has an outer shape in which extended parts 4 a are extended in respective three directions up to the vicinity of the inner surface of the casing 64, as shown in FIG. 7, which makes it easy to position the expansion valve 1 a, when inserting the same into the casing 64 and connecting the outlet port 6 to the inlet pipe 62.

FIG. 8 is a cross-sectional view showing an expansion valve according to a third embodiment of the present invention and a mounted state thereof, and FIG. 9 is a view of the expansion valve in the mounted state, taken from the inlet port side. Component elements appearing in FIGS. 8 and 9, which have functions identical to or equivalent to those of the component elements appearing in FIGS. 1 and 4, are designated by identical reference numerals, and detailed description thereof is omitted.

The expansion valve 1 b according to the third embodiment has the same construction as the expansion valve 1 according to the first embodiment in respect of the body 4, but the construction of the juncture between the power element 3 and the body is changed. More specifically, the power element 3 of the above-described expansion valves 1 and 1 a has the female thread 24 formed in the inner periphery of the hub 23 extended outward from the central opening of the lower housing 18. The female thread 24 is formed by tapping or pressing the hub 23 after the lower housing 18 is formed by pressing. Therefore, the configuration of the power element 3 of the expansion valves 1 and 1 a requires fabrication for forming the female thread 34. In contrast, the power element 3 of the expansion valve 1 b is configured such that the female thread 24 is formed simultaneously when the lower housing 18 is formed by pressing.

That is, the inner periphery of the central opening of the lower housing 18 is formed with a thread such that the thread has a cutout in an angle range of 60 degrees out of the whole circumference thereof, and is continuously displaced in the axial direction over a remaining angle of 300 degrees, and such that the axial displacement of the thread assumed to be formed over an angle range of 360 degree is substantially equal to a pitch of the male thread 16 formed on the guide 15. By thus configuring the central opening of the lower housing 18 such that it has a one-turn thread structure, the lower housing 18 can be formed by pressing in its entirety, including the female thread 24, and by combining the same with the body 4 which is formed by die-casting without requiring fabrication, the cost of the expansion valve 1 can be further reduced.

Further, in the expansion valve 1 b, the power element 3 is configured such that it has no protruded portions, to thereby make the heat insulation cover 68 simplified in shape. More specifically, the upper housing 17 has a generally outwardly inflating shape, but a central portion including the gas introducing hole 21 is formed as a recess, whereby the metal ball 22 is prevented from protruding from the outermost surface of the upper housing 17 when it closes the gas introducing hole 21.

Similarly to the expansion valve 1 according to the first embodiment, the expansion valve 1 b is mounted within the casing 64 integrally formed with the evaporator 60. In the present embodiment, the inlet pipe 62 of the evaporator 60 connected to the outlet port 6 is formed by recessing a plate forming a header part of the evaporator 60 such that the hollow cylindrical part 6 a of the outlet port 6 is fitted therein. Further, the low-pressure pipe 65 is directly connected to the casing 64 by expanding an end thereof, and using a pipe clamp 67. At this time, the connection between them is performed by fixing the casing 64 and a backup ring 69 by the pipe clamp 67, in a state where the backup ring 69 holds the casing 64, the low-pressure pipe 65, and the O ring, on the atmosphere side.

FIG. 10 is a cross-sectional view showing an expansion valve according to a fourth embodiment and a mounted state thereof, and FIG. 11 is a cross-sectional view taken on line C-C of FIG. 10. Component elements appearing in FIGS. 10 and 11, which have functions identical to or equivalent to those of the component elements appearing in FIGS. 1 and 4, are designated by identical reference numerals, and detailed description thereof is omitted.

The expansion valves 1, 1 a, and 1 b according to the first to third embodiments of the present invention are configured such that the valve element 9 acts in the valve opening direction when the inlet port 5 receives high-pressure refrigerant, whereas the expansion valve 1 c according to the fourth embodiment of the present invention is configured such that the valve element 9 acts in the valve closing direction when high-pressure refrigerant is received at the inlet port 5. Therefore, the body 4 is configured such that inside thereof, the inlet port 5 and the hole 8 receiving the valve element 9 therein communicate with each other, and the hole 12 receiving the shaft 13 therein and the outlet port 6 communicate with each other. In short, the present embodiment is configured such that the relation between the inlet port 5 and the outlet port 6 is inverted from that between those of the expansion valve 1 according to the first embodiment.

Further, in the expansion valve 1 c, the configuration of the juncture between the power element 3 and the body 4 is changed. More specifically, although the power element 3 of the above-described expansion valves 1 and 1 a is configured such that the hub 23 formed with the female thread 24 is protruded outward from the central opening of the lower housing 18, the expansion valve 1 c is configured such that the hub 23 is formed by bending inward the inner periphery of the central opening of the lower housing 18, and the inner peripheral surface of the bent portion of the hub 23 is formed with a thread. This reduces the overall height of the expansion valve 1 c to reduce the size thereof. Further, the female thread 24 can be preferably formed as a rolled thread. The rolled thread is easier to cut than the pressed thread, and hence it is possible reduce the cost of fabrication.

Further, the heat insulation cover 68 covering the power element 3 is integrally formed with fixing legs 68 a by resin-molding. Although not shown, each fixing leg 68 a have a hook formed at an end thereof, and the hook is engaged with a stepped portion formed in the body 4, whereby the heat insulation cover 68 is fixed.

Further, in the present embodiment, the manner of mounting the expansion valve 1 c is modified compared with the cases of the first to third embodiments. More specifically, in the case of the expansion valves 1, 1 a, and 1 b according to the first and third embodiments, not only the high-pressure pipe 61 and the low-pressure pipe 65 but also the inlet pipe 65 and the casing 64 are formed by a double pipe, respectively, and each of the expansion valve 1, 1 a, and 1 b is mounted in an intermediate portion of the double pipe. In contrast, in the expansion valve according to the present embodiment, the pipe upstream of the evaporator and the low-pressure pipe 65 downstream of the same are formed as separate pipes, and the expansion valve 1 c is mounted in the intermediate portions of the pipes.

The inlet pipe 62 extending from the evaporator and the low-pressure pipe 65 a have respective ends thereof integrally joined to the casing 64 e.g. by welding, and the end of the high-pressure pipe 61 opposed to that of the inlet pipe 62 and the end of the low-pressure pipe 65 b opposed to that of the low-pressure pipe 65 a are rigidly joined to a disc-shaped joint part 66 by welding. The casing 64 and the joint part 66 are connected by the pipe clamp 67. It should be noted that the pipe extending from the evaporator to the compressor passes refrigerant lower in density than refrigerant flowing through the pipe extending to the evaporator, and hence is formed to have a larger diameter than the pipe extending to the evaporator. Therefore, in the junctures where the pipes are connected, the respective sizes of the casing 64, the joint 66, and the pipe clamp 67 are increased according to the diameters of the associated pipes. In the present embodiment, however, the low-pressure pipe 65 b connected to the joint 66 has a foremost joint portion formed to have a flatted shape, as shown in FIG. 11, to thereby prevent the joint 66 from becoming larger in size. Of course, the foremost end of the low-pressure pipe 65 a connected to the casing 64 is also formed to have a flatted shape.

Although in the first to fourth embodiments described above, the body 4 is formed by die-casting of an aluminum alloy, it may be formed by injection molding of a resin or the like by using the three-way separable dies described above. As the material of the resin body, a polyphenylene sulfide (PPS) is used which is excellent in heat resistance, mechanical properties, etc. In this case, the resin has a material mixed therein which makes noise generated inside the body difficult to be transmitted to the outside.

In the expansion valve, noise is generated when refrigerant flows through a narrow gap between the valve seat and the valve element. The flow noise is externally emitted as an unusual sound, but if the material of the body is an aluminum alloy, the sound insulation and sound absorption effects thereof are high enough to prevent the externally emitted noise from being considered troublesome. However, when the material of the body is a resin, the sound insulation and sound absorption effects thereof are not so high compared with the aluminum alloy. In view of this, a material, higher in density than the resin, such as a metal powder or metal fibers of iron, brass, or copper, is mixed in the resin. As a consequence, energy of flow noise produced from the valve section is damped by the metal power or metal fibers within the body, which makes it possible to reduce sound pressure level of flow noise emitted from the body.

In the expansion valve according to the present invention, the body is formed using the forming dies, and hence an inlet port, an outlet port, a hole for receiving therein a valve element and a set value-adjusting member, a valve hole, a hole for receiving therein a member that transmits an actuating force dependent on temperature sensed by the power element to the valve element, and the thread part for having the power element connected thereto are formed integrally with the body. This is advantageous in that it is no longer necessary to subject the body to fabrication, and hence it is possible to improve the manufacturing efficiency of the body, provide a higher yield from material, and reduce the manufacturing cost of the expansion valve.

Further, in the power element as well, by forming a housing that is connected to the thread part formed on the body, in a one-turn thread configuration such that an inner peripheral edge of a central opening thereof is continuously displaced in an axial direction over an angle range of smaller than 360 degrees, the housing can be formed by pressing. This makes it unnecessary to carry out fabrication for cutting a thread, and hence it is possible further reduce the manufacturing cost of the expansion valve.

The foregoing is considered as illustrative only of the principles of the present invention. Further, since numerous modifications and changes will readily occur to those skilled in the art, it is not desired to limit the invention to the exact construction and applications shown and described, and accordingly, all suitable modifications and equivalents may be regarded as falling within the scope of the invention in the appended claims and their equivalents. 

1. An expansion valve that passes introduced refrigerant through a valve section disposed therein to thereby throttle and expand the introduced refrigerant, wherein a body accommodating said valve section is formed, using forming dies, integrally with a thread part that connects a power element thereto.
 2. The expansion valve according to claim 1, wherein said body is formed such that an axis of an inlet port for introducing refrigerant and an axis of an outlet port for delivering expanded refrigerant are identical or parallel with each other, and such that a first hole for receiving therein a valve element and a set value-adjusting member, a valve hole, and a second hole for receiving therein a member that transmits an actuating force dependent on temperature sensed by said power element to said valve element are arranged on an identical axis orthogonal to the axis of the inlet port or the axis of the outlet port, and have respective diameters reduced in a mentioned order thereof, and wherein said thread part is formed on an outer periphery of a hollow cylindrical part defining the second hole.
 3. The expansion valve according to claim 2, wherein said thread part is formed as a partial thread in which portions of an outer peripheral surface of said hollow cylindrical part facing in directions perpendicular to an identical surface or parallel surfaces including the axis of the inlet port, the axis of the outlet port, and an axis of the valve hole are not threaded.
 4. The expansion valve according to claim 1, wherein said body is formed such that an axis of an inlet port for introducing refrigerant and an axis of an outlet port for delivering expanded refrigerant are orthogonal to each other, on an identical plane including the axes or as viewed from a direction perpendicular to parallel planes respectively including the axes, and such that the inlet port or the outlet port, a valve hole, and a hole for receiving therein a member that transmits an actuating force dependent on temperature sensed by said power element to said valve element are arranged on an identical axis, and have respective diameters reduced in a mentioned order thereof, and wherein said thread part is formed on an outer periphery of a hollow cylindrical part defining the hole.
 5. The expansion valve according to claim 4, wherein said thread part is formed as a partial thread in which portions of an outer peripheral surface of said hollow cylindrical part facing in directions perpendicular to an identical surface or parallel surfaces including the axis of the inlet port, the axis of the outlet port, and an axis of the valve hole are not threaded.
 6. The expansion valve according to claim 1, wherein said power element has a one-turn thread formed such that an inner peripheral edge of a central opening of a housing on a side where said thread part is connected is continuously displaced in an axial direction over an angle range of smaller than 360 degrees.
 7. The expansion valve according to claim 1, wherein said power element has a hub formed by bending inward an inner periphery of a central opening of a housing on a side where said thread part is connected, and an inner peripheral surface of said hub is threaded.
 8. The expansion valve according to claim 1, wherein said body is formed by die-casting a metal, using dies having a three-way separable structure as the forming dies.
 9. The expansion valve according to claim 1, wherein said body is formed by resin casting, using dies having a three-way separable structure as the forming dies.
 10. The expansion valve according to claim 9, wherein the resin has a metal powder or metal fibers, larger in density than the resin, mixed therein.
 11. The expansion valve according to claim 1, wherein the expansion valve is a thermostatic expansion valve in which said body and said power element are disposed within a low-pressure pipe extending from an evaporator to a compressor, and connection of a inlet port to a high-pressure pipe through which high-pressure refrigerant is supplied, and connection of an outlet port to an evaporator inlet pipe through which expanded refrigerant is delivered toward the evaporator are established within the low-pressure pipe.
 12. The expansion valve according to claim 11, comprising a heat insulation cover configured to cover an outer housing of said power element. 